1. Make the chicken tinga: Preheat oven to 300 degrees. In a roasting pan, combine all ingredients with 1 cup water. Mix well and cover with foil. Roast until chicken is tender, about 3 hours.
2. Assemble the sandwiches: Once chicken is roasted, shred meat. Toast brioche buns, then top with sliced avocado, shredded chicken tinga, coleslaw, and pickled jalapeños.